Fresh and sea water immersion corrosion testing on marine structural steel at low temperature

The aim of the present study is to experimentally examine the corrosion progress characteristics of steel associated with fresh and sea water immersion at low temperature. Three types of steel, namely mild steel (Grade A) and high tensile steel (Grades A and D) are tested under various corrosive conditions in the fresh water, in the sea water and in the air at a temperature of 18°C, 0°C and −10°C. Mass loss of test specimen due to corrosion is measured at a monthly interval and it is converted to a loss of steel plate thickness. Based on the test database, the effects of parameters affecting the corrosion progress are discussed. Test database obtained in the present study is documented

Full-scale collapse testing of a steel stiffened plate structure under axial-compressive loading triggered by brittle fracture at cryogenic condition

This paper is a sequel to the authors’ earlier article Paik et al. [2020a. Full-scale collapse testing of a steel stiffened plate structure under cyclic axial-compressive loading, Structures, https://doi.org/10.1016/j.istruc.2020.05.026]. The aim of the paper was to present a test data on the ultimate compressive strength characteristics of a full-scale steel stiffened plate structure at cryogenic condition which may be due to unwanted release of liquefied gases. The test structure was fabricated in a shipyard using exactly the same welding technology as used in today’s shipbuilding industry. It is observed that the test structure reaches the ultimate limit states triggered by brittle fracture, which is totally different from typical collapse modes at room temperature. Details of the test database are documented as they can be used to validate computational models for the structural crashworthiness analysis involving brittle fracture at cryogenic condition

A new method for assessing the safety of ships damaged by collisions

The longitudinal strength of a ship decreases with the reduction in its bending moment capacity following a collision accident. This decrease may lead to the total loss of the ship in some cases due to its loss of hull girder strength, particularly when large vessels are involved. Therefore, the damaged ship should be able to reach the closest harbour safely without any catastrophic hull girder collapse. This paper aims to develop a method to predict the hull girder residual strength of double-hull oil tankers by considering probabilistic collision damage scenarios. The collision damage index is defined as the reduction ratio of the vertical hull girder moment of inertia, and the residual strength index is characterised as the reduction ratio of the hull girder ultimate bending moment. Four different as-built double-hull oil tankers (Panamax, Aframax, Suezmax and VLCC) were studied to demonstrate the proposed method and to formulate the collision damage index. The relationships between the residual strength index and the collision damage index are identified in the form of diagrams and linear-type regressions. The produced diagrams and regressions represent a first-cut assessment of a ship’s safety immediately after taking collision damage

Seed-layer mediated orientation evolution in dielectric Bi-Zn-Ti-Nb-O thin films

Highly (hhh) -oriented pyrochlore Bi-Zn-Ti-Nb-O (BZTN) thin films were fabricated via metal-organic decomposition using orientation template layers. The preferred orientation was ascribed to the interfacial layer, the lattice parameter of which is similar to BZTN. High-resolution transmission electron microscopy supported that the interfacial layer consists of Bi and Pt. The (hhh) -oriented thin films exhibited a highly insulating nature enabling feasible applications in electronic devices, particularly voltage tunable application. The BZTN thin films did not show any apparent dielectric anisotropy and the slightly enhanced dielectric properties were discussed in connection to the internal stress and the grain boundary effect. © 2007 American Institute of Physics

Minimum-Uncertainty Angular Wave Packets and Quantized Mean Values

Uncertainty relations between a bounded coordinate operator and a conjugate momentum operator frequently appear in quantum mechanics. We prove that physically reasonable minimum-uncertainty solutions to such relations have quantized expectation values of the conjugate momentum. This implies, for example, that the mean angular momentum is quantized for any minimum-uncertainty state obtained from any uncertainty relation involving the angular-momentum operator and a conjugate coordinate. Experiments specifically seeking to create minimum-uncertainty states localized in angular coordinates therefore must produce packets with integer angular momentum.Comment: accepted for publication in Physical Review

Anisotropic Terahertz Emission from Bi2Se3 Thin Films with Inclined Crystal Planes

We investigate the surface states of topological insulator (TI) Bi2Se3 thin films grown on Si nanocrystals and Al2O3 substrates by using terahertz (THz) emission spectroscopy. Compared to bulk crystalline Bi2Te2Se, film TIs exhibit distinct behaviors in the phase and amplitude of emitted THz radiation. In particular, Bi2Se3 grown on Al2O3 shows an anisotropic response with a strong modulation of the THz signal in its phase. From x-ray diffraction, we find that the crystal plane of the Bi2Se3 films is inclined with respect to the plane of the Al2O3 substrate by about 0.27 degrees. This structural anisotropy affects the dynamics of photocarriers and hence leads to the observed anisotropic response in the THz emission. Such relevance demonstrates that THz emission spectroscopy can be a sensitive tool to investigate the fine details of the surface crystallography and electrostatics of thin film TIs.1112Ysciescopu

Rapid hull collapse strength calculations of double hull oil tankers after collisions

The primary objective of this study is to develop a rapid method for calculating hull collapse strength of double hull oil tankers after collisions. For this purpose, the statistical characteristics of hull girder collapse after collision are studied. Four double hull oil tankers with different size are considered: Panamax, Aframax, Suezmax and Very Large Crude Carrier. A set of 50 credible collision scenarios are selected by a sampling technique associated with the collision hazard identification based on the historical ship collision database. Four parameters, namely vertical collision location, damage penetration, striking ship's bulbous bow height, and striking ship's bulbous bow length are determined as a consequence of the corresponding collision scenario. The intelligent supersize finite element method is used to compute the progressive collapse behaviour of hull girder structures with the collision damages so determined. The residual hull girder strength indices can then be determined and formulated in a closed expression associated with collision damages and ship length. The developed formulations will be useful to quickly calculate the hull collapse strength of double hull oil tankers immediately after collisions

Long-term annual primary production in the Ulleung Basin as a biological hot spot in the East/Japan Sea

Although the Ulleung Basin is an important biological hot spot in East/Japan Sea (hereafter the East Sea), very limited knowledge for seasonal and annual variations in the primary productivity exists. In this study, a recent decadal trend of primary production in the Ulleung Basin was analyzed based on MODIS-derived monthly primary production for a better annual production budget. Based on the MODIS-derived primary production, the mean daily primary productivity was 766.8 mg C m-2 d-1 (SD=+/- 196.7 mg C m-2 d-1) and the annual primary productivity was 280.2 g C m-2 yr-1 (SD=+/- 14.9 g C m-2 yr-1) in the Ulleung Basin during the study period. The monthly contributions of primary production were not largely variable among different months, and a relatively small interannual production variability was also observed in the Ulleung Basin, which indicates that the Ulleung Basin is a sustaining biologically productive region called as hot spot in the East Sea. However, a significant recent decline in the annual primary production was observed in the Ulleung Basin after 2006. Although no strong possibilities were found in this study, the current warming sea surface temperature and a negative phase PDO index were suggested for the recent declining primary production. For a better understanding of subsequent effects on marine ecosystems, more intensive interdisciplinary field studies will be required in the Ulleung Basin

Magnetic Origin of Giant Magnetoelectricity in Doped Y-type Hexaferrite Ba0.5Sr1.5Zn2(Fe1-xAlx)(12)O-22

We investigated site-specific magnetic behaviors of multiferroic Ba0.5Sr1.5Zn2(Fe1-xAlx)(12)O-22 using Fe L-2,L-3-edge x-ray magnetic circular dichroism. The Al dopants mostly replace the Fe3+ ions at octahedral (O-h) sites, which contribute unquenched angular momenta through off-centering displacements. This replacement greatly reduces the magnetic anisotropy energy to change the magnetic order from a helical to a heliconical type with enhanced magnetoelectric susceptibility (alpha(ME)). The tetrahedral (T-d) Fe sites exhibit magnetic hysteresis distinguishable from that of the O-h sites, especially at low magnetic fields. These results provide essential clues for the heliconical order with a giant aME and multibit memory effects in the Al-doped Y-type hexaferrite.open1178sciescopu